"Reagan" is used as a first name. I found the following on a site that lists 'Girl's Names':
Regan little king, counselor・ Reagan, Raegan, Ragan, Reagann, Regann, Reganne. Powerful, commanding, Regan is one heck of a name for a little girl. Not only do you have the imposing sound of the name itself, you also have the associations that come along with President Reagan as well as one of the evil sisters from King Lear and the slime-spewing kid in The Exorcist.